Dielectric properties of polyarylate blends

Dielectric properties and molecular motion were studied by use of dielectri c spectroscopy and differential scanning calorimetry for two blends, fully transesterificated polyarylate of bisphenol A with terephthalate/isophthala te (50/50) (PA)/polycarbonate of bisphenol A (PC) blends and PA/poly(ethyle ne terephthalate) (PET) blends. All the quenched PA/PC and PA/PET blends we re amorphous and the glass transition temperature (Tg) was varied with the blends ratio according to Gordon-Taylor equation. The PA/PET blends with mo re than 60% of PET crystallized above the crystallization temperature. The PA/PC and PA/PET blends showed two dielectric relaxations, alpha above Tg a nd gamma below Tg, which are related to a glass transition and a local moti on of short segment, respectively. The alpha relaxation moved to lower temp eratures as PC or PET content increases, reflecting the lowering Tg faithfu lly. In the PA/PET blends, the static (epsilon(0)) and the limiting dielect ric constant (epsilon(infinity)), and the increment (Delta epsilon) for the alpha relaxation decreases with increasing temperature and the decrease fa lled on one curve, independent of the blend ratio. Any ferro- and piezoelec tricity were not observed for two blends. (C) 2000 Kluwer Academic Publishe rs.